The Applicant is the owner and inventor of U.S. Pat. No. 5,056,471 the present invention generally relates to internal combustion engines having reciprocating pistons. More specifically this invention relates to an Internal Combustion Engine having designated combustion exhaust cylinders, through which a double expansion system is implemented for deriving work from the combustion exhaust gases of the combustion cylinders. Description of Prior Art Internal combustion (IC) engines currently are by far The predominant engine form used today for purposes of providing power to propel motorized vehicles, as well as many other forms of transportation and recreation devices.
The (IC) engine is preferred, for it""s exceptional power and weight ratio and energy storage potential (miles traveled between refueling), when compared to other comparable forms of automotive power. However, concern for the environment and preservation of natural resources has continuously encouraged efforts to improve the efficiency, performance and fuel economy of (IC) engines while reducing their noxious emissions and noise. Several arrangements have been suggested to improve (IC) engine efficiency by providing intercooperating cylinders having different functions. Included in other prior arts known to me are eleven inventions which pertain to internal combustion engines having reciprocating pistons some what related to the engine of the present invention but which differ therefrom in operation and/or structure to a considerable degree. One example of this approach is shown in U.S. Pat. No. 2,196,228 to Prescott. Prescott discloses pairs of high pressure and low pressure cylinders in which an air/fuel mixture is combusted in the primary high pressure cylinder and exhausted to a low pressure cylinder to raise thermal efficiency. No air/fuel mixture is combusted in the low-pressure cylinder to produce additional power.
Another example of this approach is shown in U.S. Pat. No. 4,237,832 to Hartig. Hartig discloses a Partial load control apparatus and method for internal combustion engines. Where with decreasing load, high-pressure combustion cylinders are changed over to low pressure after expansion cylinders, No additional work is provided to the engine from the high-pressure cylinders from incompletely expanded combustion gases of low-pressure cylinders.
Another example of this approach is shown in foreign patent No.128921 to Shimizu. Shimizu discloses a pair of cylinders in which an air/fuel mixture is combusted in the first cylinder and exhausted to a second cylinder, which provides additional power to the crankshaft of the internal combustion engine in a two-stroke cycle. No air/fuel mixture is combusted in the second cylinder to produce additional power to the crankshaft.
The advantage to this arrangement is providing additional power to the crankshaft of the IC engine without burning additional fuel. The disadvantage is no additional power is delivered to the second cylinder without the combustion of additional fuel as compared to a comparably sized IC engine.
According to the present invention there is provided an IC engine having at least two cylinders, generally referred to as a first cylinder and a second cylinder, respectively, which reciprocally reside within their respective cylinders. The first and second pistons are reciprocated by any conventional means, such as an engine crankshaft, between top dead center (TDC), where they are furthest from the crankshaft axis, and bottom dead center (BDC) at which time they are at their nearest point to the crankshaft axis. The second piston is timed by the crankshaft. Leading the first piston by a predetermined crankshaft angle such that the second piston is retreating from TCD when the first piston is retreating from BDC. The first cylinder has a first cylinder intake port and a first cylinder exhaust port. A fluidic passageway connects the exhaust port of the first cylinder with the exhaust port of the second cylinder.
The first cylinder intake port is open by the first cylinder intake valve, during the intake stroke of the first cylinder. But is otherwise closed during the first cylinder""s compression stroke, first cylinder""s power stroke, first cylinder""s exhaust stroke and first cylinder""s intake power stroke.
The first cylinder also has a first cylinder exhaust port, which is open by the first cylinder exhaust valve, during the first cylinder""s exhaust strokes. But otherwise closed during the first cylinder""s intake stroke, first cylinder""s compression stroke, first cylinder""s power stroke first cylinder""s intake power stroke.
The first cylinder is also in communication with a third exhaust port, which is opened by a third exhaust valve. The third exhaust valve is open During the first cylinder""s exhaust stroke to atmosphere, but otherwise closed during the transfer of exhaust gases from one cylinder to the other during the intake power stroke of the first cylinder.
A second cylinder is also provided with a second cylinder intake port and a second cylinder exhaust port. The second cylinder intake port is open by the second cylinder intake valve during the intake stroke of the second cylinder""s piston. But is otherwise closed during the second cylinder""s compression stroke, second cylinder""s power stroke, second cylinder""s exhaust stroke, second cylinder""s intake power stroke.
The second cylinder also has a second cylinder exhaust port, which is open by the second cylinder exhaust valve during the second cylinders exhaust strokes. But is otherwise closed during the second cylinder""s intake stroke, second cylinder""s compression stroke, second cylinder""s power stroke and second cylinder""s intake power stroke.
The second cylinder is also in communication with a third exhaust port, which is opened by a third exhaust valve. The third exhaust valve is open, During the second cylinder""s exhaust strokes to atmosphere, but otherwise closed during the transfer of exhaust gases from one cylinder to the other during the intake power stroke of the second cylinder. A fluidic passage is provided between the first cylinder exhaust port, the second cylinder exhaust port and the third exhaust port for purposes to be explained later.
In operation of the IC engine, a combustible air/fuel mixture is drawn into the first cylinder through the first cylinder""s intake valve during the intake stroke of the first cylinder""s piston. The combustible fuel mixture is then compressed within the first cylinder during the first cylinder""s compression stroke and is ignited just prior to TDC at the end of the first cylinder""s compression stroke.
Ignition is accomplished by any suitable igniter, such as a conventional engine spark plug. Upon ignition, the combustible fuel mixture produces combustion gasses within the first cylinder. The expansion of the combustion gasses drives the first cylinder""s piston toward BDC during the first cylinder""s power stroke, and the gasses are expelled from the first cylinder during the first cylinder""s exhaust stroke. The combustion gasses exit the first cylinder via it""s first cylinder exhaust port and flow through the fluidic passage to the second cylinder, entering the second cylinder through the second cylinder exhaust port.
The combustion gasses are received by the second cylinder at the start of the second cylinder""s intake power stroke. The timing between the first cylinder""s piston and the second cylinder""s piston, is such that the combustion gasses exert a force on the second cylinder""s piston and drives the second cylinder""s piston toward BDC. From there the combustion gasses are expelled from the second cylinder through the second cylinder exhaust port and out to atmosphere through the third exhaust port during the second cylinder""s exhaust stroke.
A combustible air/fuel mixture is drawn into the second cylinder through the second cylinder""s intake valve during the intake stroke of the second cylinder""s piston. The combustible fuel mixture is then compressed within the second cylinder, during the second cylinder""s compression stroke and is ignited just prior to TDC at the end of the second cylinder""s compression stroke. Ignition is accomplished by any suitable igniter, such as a conventional engine spark plug. Upon ignition, the combustible fuel mixture produces combustion gasses within the second cylinder. The expansion of the combustion gasses drives the second cylinder""s piston toward BDC during the second cylinder""s power stroke, the gases are expelled from the second cylinder during the second cylinder""s exhaust stroke. The combustion gasses exit the second cylinder via it""s second cylinder exhaust port and flow through the fluidic passage to the first cylinder, entering the first cylinder through the first cylinder exhaust port. The combustion gasses are received by the first cylinder at the start of the first cylinder""s intake power stroke.
The timing between the second cylinder""s piston and the first cylinder""s piston is such that the combustion gasses exert a force, on the first cylinder""s piston and drives the first cylinder""s piston toward BDC. From there the combustion gasses are expelled from the first cylinder through the first cylinder exhaust port and out to atmosphere through the third exhaust port during the first cylinder""s exhaust stroke.
The timing of the first cylinder and second cylinder is such that the engine receives three power strokes every five revolutions per cylinder. Two conventional four-stroke power strokes and one exhaust power stroke, which will be discussed later with the preferred embodiment and timing diagrams. Overall this preferred embodiment allows each cylinder to alternate between burning fuel to power the piston in each cylinder and using exhaust gases to power the piston in each cylinder in a four-stroke IC engine cycle.
In, contrast, operation of a two-stroke cycle allows the combustion of an air/fuel mixture in each cylinder and is timed such that the engine receives two power strokes every three revolutions per cylinder. One conventional two-stroke power stroke and one exhaust power stroke. This preferred embodiment allows each cylinder to alternate between burning fuel to power the pistons and using exhaust gases to power the pistons. Which will be discussed later with the preferred embodiment and timing diagrams.
According to a preferred aspect of the present invention, an advantageous feature is that the combustion gasses of the first and second cylinder are not merely exhausted to atmosphere, but are directly used to derive additional work from the engine. As a result, the output torque of an IC engine in accordance with the present invention is greater than that of comparably sized IC engine having the same number of cylinders and combusting the same quantity of fuel. Balance of the engine is more stable due to the alternating combustion of fuel in each cylinder over comparable double expansion engines.
In addition, a significant advantage of the present invention is that, by reducing the amount of fuel burning cycles pollutants can be greatly reduced and fuel economy increased in comparison to a conventional IC engine.
It is further object of this invention that such an engine more effectively utilizes the energy potential within the combustion exhaust gasses that would otherwise be lost by exhausting to atmosphere. Other objects and advantages of this invention will be more apparent after reading of the following detailed description taken in conjunction with the drawings provided.